The Dynamic Host Configuration Protocol (DHCP) enables assignment of dynamic Internet Protocol (IP) addresses to devices on a network. Such dynamic assignment of IP addresses simplifies network administration. In particular, there is no need for an administrator to manually manage and coordinate unique IP addresses among the devices. Rather, with the use of DHCP, such management and coordination occurs in an automated manner.
Typically, when a DHCP client (e.g., a networked computer) is first switched on, the DHCP client sends a broadcast packet on the network with a DHCP request. A DHCP server on the network then detects this packet, and assigns an IP address to that DHCP client from a pool of available IP addresses for a “leased” amount of time. When the lease is about to expire, the DHCP client may renew the lease for that IP address. However, if the DHCP server does not hear from the DHCP client beyond the expiry of the lease period, the DHCP server typically places the IP address back into the pool ready to be re-used.
Some DHCP servers are equipped to accommodate DHCP requests from a device that has been statically pre-assigned an IP address. That is, the DHCP server has been configured to assign a pre-assigned IP address to the device, rather than assigning an IP address to the device from a pool of available IP addresses. If the DHCP server receiving the DHCP request from the device authenticates the DHCP client (e.g., by MAC address matching), the DHCP server assigns the pre-assigned IP address to the DHCP client. However, if the DHCP server determines that the DHCP server does not have a pre-assigned IP address for the device, the DHCP server dynamically assigns an IP address to the device from a pool of IP addresses that area available for dynamic assignment.